Multimodal single-cell analysis reveals distinct radioresistant stem-like and progenitor cell populations in murine glioma.

Radiation therapy is part of the standard of care for gliomas and kills a subset of tumor cells, while also altering the tumor microenvironment. Tumor cells with stem-like properties preferentially survive radiation and give rise to glioma recurrence. Various techniques for enriching and quantifying cells with stem-like properties have been used, including the fluorescence activated cell sorting (FACS)-based side population (SP) assay, which is a functional assay that enriches for stem-like tumor cells. In these analyses, mouse models of glioma have been used to understand the biology of this disease and therapeutic responses, including the radiation response. We present combined SP analysis and single-cell RNA sequencing of genetically-engineered mouse models of glioma to show a time course of cellular response to radiation. We identify and characterize two distinct tumor cell populations that are inherently radioresistant and also distinct effects of radiation on immune cell populations within the tumor microenvironment.

Post-menopausal presentation of yolk sac germ cell tumour.

•Yolk sac germ cell tumours are rare in post-menopausal patients.•Most involve mixed yolk sac tumours•Consider diagnosis in patients with a pelvic-abdominal mass and raised AFP.

Serum response factor promotes resilience to chronic social stress through the induction of DeltaFosB.

The molecular mechanisms underlying stress- and drug-induced neuronal adaptations are incompletely understood. One molecule implicated in such adaptations is ΔFosB, a transcription factor that accumulates in the rodent nucleus accumbens (NAc), a key brain reward region, in response to either chronic stress or repeated exposure to drugs of abuse. The upstream transcriptional mechanisms controlling ΔFosB induction by these environmental stimuli remain elusive. Here, we identify the activity-dependent transcription factor, serum response factor (SRF), as a novel upstream mediator of stress-, but not cocaine-, induced ΔFosB. SRF is downregulated in NAc of both depressed human patients and in mice chronically exposed to social defeat stress. This downregulation of SRF is absent in resilient animals. Through the use of inducible mutagenesis, we show that stress-mediated induction of ΔFosB, which occurs predominantly in resilient mice, is dependent on SRF expression in this brain region. Furthermore, NAc-specific genetic deletion of SRF promotes a variety of prodepressant- and proanxiety-like phenotypes and renders animals more sensitive to the deleterious effects of chronic stress. In contrast, we demonstrate that SRF does not play a role in ΔFosB accumulation in NAc in response to chronic cocaine exposure. Furthermore, NAc-specific knock-out of SRF has no effect on cocaine-induced behaviors, indicating that chronic social defeat stress and repeated cocaine exposure regulate ΔFosB accumulation and behavioral sensitivity through independent mechanisms.

DeltaFosB in brain reward circuits mediates resilience to stress and antidepressant responses.

In contrast with the many studies of stress effects on the brain, relatively little is known about the molecular mechanisms of resilience, the ability of some individuals to escape the deleterious effects of stress. We found that the transcription factor DeltaFosB mediates an essential mechanism of resilience in mice. Induction of DeltaFosB in the nucleus accumbens, an important brain reward-associated region, in response to chronic social defeat stress was both necessary and sufficient for resilience. DeltaFosB induction was also required for the standard antidepressant fluoxetine to reverse behavioral pathology induced by social defeat. DeltaFosB produced these effects through induction of the GluR2 AMPA glutamate receptor subunit, which decreased the responsiveness of nucleus accumbens neurons to glutamate, and through other synaptic proteins. Together, these findings establish a previously unknown molecular pathway underlying both resilience and antidepressant action.

Antidepressant actions of histone deacetylase inhibitors.

Persistent symptoms of depression suggest the involvement of stable molecular adaptations in brain, which may be reflected at the level of chromatin remodeling. We find that chronic social defeat stress in mice causes a transient decrease, followed by a persistent increase, in levels of acetylated histone H3 in the nucleus accumbens, an important limbic brain region. This persistent increase in H3 acetylation is associated with decreased levels of histone deacetylase 2 (HDAC2) in the nucleus accumbens. Similar effects were observed in the nucleus accumbens of depressed humans studied postmortem. These changes in H3 acetylation and HDAC2 expression mediate long-lasting positive neuronal adaptations, since infusion of HDAC inhibitors into the nucleus accumbens, which increases histone acetylation, exerts robust antidepressant-like effects in the social defeat paradigm and other behavioral assays. HDAC inhibitor [N-(2-aminophenyl)-4-[N-(pyridine-3-ylmethoxy-carbonyl)aminomethyl]benzamide (MS-275)] infusion also reverses the effects of chronic defeat stress on global patterns of gene expression in the nucleus accumbens, as determined by microarray analysis, with striking similarities to the effects of the standard antidepressant fluoxetine. Stress-regulated genes whose expression is normalized selectively by MS-275 may provide promising targets for the future development of novel antidepressant treatments. Together, these findings provide new insight into the underlying molecular mechanisms of depression and antidepressant action, and support the antidepressant potential of HDAC inhibitors and perhaps other agents that act at the level of chromatin structure.

Evaluation of a statistically derived decision tree for the cytodiagnosis of fine needle aspirates of the breast (FNAB).

A decision tree for the diagnosis of FNAB was derived from defined human observations using a rule induction method, C4.5 (a derivative of the ID3 algorithm). This algorithm is an implementation of the top-down induction method where the tree is determined iteratively by adding those nodes and branches which maximize the information gain at each step. The tree was derived from a training set of 200 FNAB with known outcome using 10 defined features (from one observer) and patient age. The tree contained a total of seven nodes (six observable features and patient age) with eight endpoints (four benign, four malignant). The tree was applied to a test set of 400 further FNAB with observations from the training observer and produced a sensitivity of 95%, specificity of 93% and a positive predictive value (PPV) of a malignant result of 89%. Four trainee pathologists were given a training session on the observable features and then used the tree to determine outcome in a further 50 FNAB. The observers were blind to clinical details apart from age and the endpoints were coded with letters and not labelled benign or malignant. The results from these observers produced ranges of sensitivity 80-96%, specificity 64-92%, PPV 73-92% and kappa statistics (with known outcome) 0.6-0.8. Reported difficulties in using the tree included estimation of nuclear size. These results were worse than the performance of the observers on a further 50 cases without using the decision tree (sensitivity 80-100%, specificity 72-100%, PPV 78-100%, kappa 0.72-0.92). The original 50 case test set was rerandomized and the four trainee observers made all 10 defined observations on each specimen without using the decision tree; these observations were then used to derive decisions from the tree. The performance from this method was similar to that using selected features from the tree, suggesting that observation of all features together does not improve the reliability of each specific observation. The poor performance of this tree suggests that this methodology may be unsuitable for producing decision support aids for diagnostic or training purposes in this domain.

Lipid rich rhabdomyosarcoma.

A lipid rich rhabdomyosarcoma of the paratesticular region was studied by light microscopy, histochemistry, immunohistochemistry and electron microscopy. The tumour was composed of primitive looking, vacuolated, and pleomorphic cells. Lipid was present in varying amounts in all cells but was especially abundant in the vacuolated and pleomorphic cells. Some cells showed eosinophilic fibrillary cytoplasm but cross-striations were not seen. Tumour cells were positive for desmin, muscle specific actin, and vimentin. A few cells were myoglobin positive. At electron microscopy, the presence of lipid was confirmed, while thick and thin filaments, Z disks, lamina and glycogen were observed, thereby confirming striated muscle differentiation. Although moderate amounts of lipid can be expected in almost any tumour, lipid rich rhabdomyosarcomas have received little attention. The present report provides a comprehensively examined case of such a tumour initially presenting diagnostic difficulty because of its possible confusion with liposarcoma.

Chronic giardiasis of the stomach.

Two cases of chronic giardiasis of the stomach diagnosed from gastric mucosal biopsy specimens are reported. The first case was associated with an acute-on-chronic gastritis and Helicobacter-like organisms, and the second with an adenocarcinoma of the stomach. In both cases the trophozoites had been missed in earlier biopsy specimens. As far as is known this is the first report of giardiasis of the stomach.

A neuroendocrine cause of oncogenic osteomalacia.

All definite cases of oncogenic osteomalacia have, until now, been classified as mesenchymal tumours. We report here a case of oncogenic osteomalacia caused by a spinal tumour. Microscopically, it resembled the mixed connective tissue variant of previously described phosphaturic tumours. Immunohistochemical studies, however, showed the tumour cells to be positive for low molecular weight cytokeratin (CAM 5.2), S100 protein, PGP 9.5, and synaptophysin. Electron microscopy demonstrated neurosecretory granules. The histopathological findings strongly suggest that this is a neuroendocrine tumour.

Intracytoplasmic lumina--a useful diagnostic feature of adenocarcinomas.

The monoclonal antibody NCRC-11, which has epithelial membrane antigen (EMA)-like immunoreactivity, was used to identify intracytoplasmic lumina in a series of 105 adenocarcinomas from various sites and in 283 breast carcinomas; 55% of the non-breast carcinomas and all breast carcinomas except one of spindle cell type contained intracytoplasmic lumina. The highest frequency (16.4% of tumour cells) was found in invasive lobular carcinoma of the breast. The use of antibodies with EMA reactivity is advocated in the routine investigation of metastatic and undifferentiated tumours.